6.31.3 ARC Function Attributes

These function attributes are supported by the ARC back end:

interrupt

Use this attribute to indicate that the specified function is an interrupt handler. The compiler generates function entry and exit sequences suitable for use in an interrupt handler when this attribute is present.

On the ARC, you must specify the kind of interrupt to be handled in a parameter to the interrupt attribute like this:

          void f () __attribute__ ((interrupt ("ilink1")));

Permissible values for this parameter are: ilink1 and ilink2 for ARCv1 architecture, and ilink and firq for ARCv2 architecture.

long_call

medium_call

short_call

These attributes specify how a particular function is called. These attributes override the -mlong-calls and -mmedium-calls (see ARC Options) command-line switches and #pragma long_calls settings.

For ARC, a function marked with the long_call attribute is always called using register-indirect jump-and-link instructions, thereby enabling the called function to be placed anywhere within the 32-bit address space. A function marked with the medium_call attribute will always be close enough to be called with an unconditional branch-and-link instruction, which has a 25-bit offset from the call site. A function marked with the short_call attribute will always be close enough to be called with a conditional branch-and-link instruction, which has a 21-bit offset from the call site.

jli_always

Forces a particular function to be called using jli instruction. The jli instruction makes use of a table stored into .jlitab section, which holds the location of the functions which are addressed using this instruction.

jli_fixed

Identical like the above one, but the location of the function in the jli table is known and given as an attribute parameter.

secure_call

This attribute allows one to mark secure-code functions that are callable from normal mode. The location of the secure call function into the sjli table needs to be passed as argument.

naked

This attribute allows the compiler to construct the requisite function declaration, while allowing the body of the function to be assembly code. The specified function will not have prologue/epilogue sequences generated by the compiler. Only basic asm statements can safely be included in naked functions (see Basic Asm). While using extended asm or a mixture of basic asm and C code may appear to work, they cannot be depended upon to work reliably and are not supported.